HSC Science (General) 12th Standard Board Exam - Maharashtra State Board Important Questions

Derive an expression for e.m.f. and current in terms of turns ratio

In series LCR circuit at resonance, phase difference between current and e.m.f. of source is ______.

(A) `pi` rad

(B) `pi/2` rad

(C) `pi/4` rad

(D) zero rad

Prove theoretically  (electromagnetic induction) `e = (dphi)/(dt)`

Obtain an expression for the induced e.m.f. in a coil rotating with uniform angular velocity in
uniform magnetic field. Plot a graph of variation of induced e.m.f. against phase (Θ = ωt) over one cycle.

If ‘R’ is the radius of dees and ‘B’ be the magnetic field of induction in which positive charges (q) of mass (m) escape from the cyclotron, then its maximum speed (vmax) is _______.

A) `(qR)/(Bm)`

B)`(qm)/(Br)`

C) `(qBR)/m`

D) `m/(qBR)`

A transformer converts 240 V AC to 60 V AC. The secondary has 75 turns. The number of turns in primary are _______.

(A) 600

(B) 500

(C) 400

(D) 300

Define coefficient of mutual induction. 

Explain the phenomenon of mutual induction.

Write the SI unit and dimention of of co-efficient of self induction

A capacitor of capacitance 0.5 μF is connected to a source of alternating e.m.f. of frequency 100 Hz. What is the capacitive reactance? (Π = 3.142)

At which position of the plane of the rotating coil with the direction of magnetic field, the e.m.f. induced in the coil is maximum?

Answer the following:

State the principles of the electric motor and electric generator. 

Choose the correct option:

A conductor rod of length (l) is moving with velocity (v) in a direction normal to a uniform magnetic field (B). What will be the magnitude of induced emf produced between the ends of the moving conductor?

When an AC source is connected to an ideal inductor show that the average power supplied by the source over a complete cycle is zero.

Derive an expression for the impedance of an LCR circuit connected to an AC power supply. Draw phasor diagram.

A 25 μF capacitor, a 0.10 H inductor, and a 25Ω resistor are connected in series with an AC source whose emf is given by e = 310 sin 314 t (volt). What is the frequency, reactance, impedance, current, and phase angle of the circuit?

Explain the principle of operation of a photodiode.

Why are the emitter, the base, and the collector of a BJT doped differently?

The common-base DC current gain of a transistor is 0.967. If the emitter current is 10mA. What is the value of base current?

In a common-base connection, a certain transistor has an emitter current of 10mA and a collector current of 9.8 mA. Calculate the value of the base current.